1. Field of the Invention
The present invention relates to technology for calibrating ink ejection amount for a printer that forms ink dots on a printing medium while scanning a printing head unit in the main scan direction.
2. Description of the Related Art
Inkjet printers print images by ejecting ink from nozzles provided on a printing head. The same as with other types of printers, for inkjet printers as well, there is always a pursuit of improvements in quality and improvements in printing speed. In recent years, the inkjet printer image quality has improved at about the same level as silver salt photographs, so improvement of the printing speed is a bigger problem.
To improve printing speed, the easiest measure is to increase the number of nozzles per color. As a method of increasing the nozzle count, it is possible to use a plurality of printing heads, for example.
However, the ink ejection amount from a printing head nozzle ordinarily includes manufacturing errors. JP5-162338A and JP10-795A each describes a method of calibrating ink ejection amount that takes this kind of error into consideration.
With these methods, ink amount calibration is performed by calibrating the ejection amount with respect to each of the nozzles. However, sufficient mechanisms were not implemented for calibration of ink ejection amount for printers that have a plurality of printing heads. Also, this kind of problem is not limited to printers that use a plurality of printing heads, but generally is a problem that is common to printers that comprise a printing head unit that has a plurality of nozzle arrays for ejecting same ink (called a “same ink nozzle array”).